An improved practice for the production of coiled sheet metal strip material is described in U.S. Pat. Nos. 4,170,691; 4,173,313 and 4,155,238 granted Oct. 9, 1979, Nov. 6, 1979 and May 22, 1979, respectively, to applicant herein. According to this improved practice an elongated web of sheet metal is slit along parallel lines in a manner that produces parting lines containing intermittently spaced residuums of only partially sheared metal that bridge the parting line between adjacent strips and interconnect their facing edges. Thus, upon coiling of the slit product there results a wound construct containing a plurality of coiled strips integrally joined by frangible connections or tabs defined by the aforementioned partially sheared residuums of metal.
Constructs produced hereby facilitate shipment and handling of the contained coiled strips since the need to band individual strips as had theretofore been required is avoided. Also, the danger of distorting or marring the edges of individual strips is prevented due to the fact that only the endmost strips are exposed to the danger of damage during handling of the construct.
Detachment of individual strips from the construct can be effected by specialized breakaway devices by means of which a coiled strip is separated intact from the construct by the simultaneous fracture of the tabs connecting the strip thereto. One such device is described in U.S. Pat. No. 4,195,759 granted Apr. 1, 1980. Some applications, however, contemplate peeling individual strips from the construct as, for example, while the construct is rotated and a single strip is fed to a processing station such as a press or punch or the like. In U.S. Pat. No. 4,170,691, there is shown and described a prizing blade that operates to detach individual strips from the construct by shearing the connecting tabs as each strip is peeled from the construct. The described prizing blade is fixedly positioned in alignment with the parting line containing the tabs to be severed and cuts the tabs as each is successively drawn to the blade while the construct is rotated and the strip peeled therefrom.
Detaching the strips in this manner has been determined to be commercially unacceptable, especially when the sheet metal material being operated on is of reduced thickness. This is due to the fact that impacting the tabs upon the blade as is required to effect severance produces bending forces resulting in distortion of the adjacent strip material and otherwise damages the strip thereby precluding its commercial acceptability.
In U.S. Pat. No. 4,170,691 there is also described another form of strip-detaching tool in which the tabs are severed by paying the strip to be separated over a wedge-shaped prizing blade which lifts the object strip with respect to the adjacent strip in order to fracture the interconnecting tabs. Use of this form of tool produces a generally upward force vector at the tab which, due to the fact that the adjacent coils and, concomitantly, the tabs are moving translates into a force system causing the tabs to fracture in torsion thereby producing a cup and point residue that is characteristic of this type of failure. Such residue appears as burrs on the resultant strip and is unacceptable in product of a commercial grade.
It is the solution of the aforementioned problems therefore that the present invention is directed.